This invention relates to the treatment of hose and more particularly to the feeding of limp, elastomeric hose into a pressurized treatment zone.
In many elastomeric hose manufacturing processes, high temperature and pressure are required. In elastomeric hose treatments such as curing, high pressure is sometimes required to prevent blowing, blistering or other hose defects. High temperature of the pressurizing medium is, of course, required to effect a cure. To create a high temperature and pressure atmosphere in a hose process such as curing, a liquid environment, for example a type of oil, is sometimes used.
Elastomeric hose is usually built on a flexible, solid rubber form or mandrel. One purpose of the mandrel is to support the hose from the inside during its cure, thereby preventing blowing or blistering on the inside of the hose and assuring a proper inside diameter of the hose. Hose may be cured by either "batch" processes or "continuous" processes.
One "batch" method comprises taking a length or lengths of elastomeric hose and placing them in a curing zone such as an oven or vat. The designated lengths of hose can be cut and cured in a linear configuration or can be coiled around a drum or spool before curing. Because of the high pressure required, the curing zone must be completely sealed from the outside environment.
Sealing the curing zone in known batch methods presently poses no serious problems. Furthermore, there are not great handling problems with the batch method, since each batch of hose is handled only when it is placed in and removed from the curing zone. A clear disadvantage of the batch method is the labor and equipment required to handle each batch and the shut-down time of the treatment apparatus between each batch.
In "continuous" methods of curing elastomeric hose, the end of a length of hose is fed into a curing zone and is constantly moved through the curing zone, the remainder of the length following behind it. Theoretically, an endless length of hose can be processed with only one initial continuous feeding procedure. Significant reductions in labor and time required are thereby achieved, thus increasing the productivity of the apparatus.
One continuous hose processing method suggested in U.S. Pat. No. 3,475,397 is helical path curing process and apparatus. This method suggests using a hot, oily liquid to cure and to move the hose through the curing zone. Problems can arise, however, if such liquid is pressurized. Some type of inlet seal is required to maintain the pressurized liquid in the curing zone while simultaneously allowing continuous admittance of the uncured elastomeric hose. It should be noted that, although uncured elastomeric hose is sometimes processed while on a flexible mandrel, it is still extremely limp and highly susceptible to damage due to handling. Safety problems have also existed with such pressurized systems. If the inlet seal should fail, the hot, pressurized oil used in many cure processes can escape, possibly injuring persons or damaging nearby equipment.
Further problems exist with a continuous hose curing process in that the hose must be handled essentially continuously throughout the process. For example, feeding the hose into the curing zone requires a continuous feeding force applied to the portion of the hose entering the curing zone. Excessive feeding forces may be required to overcome the resistant forces applied to the hose by the pressure in the treatment zone and by the inlet seal. The aforementioned problems of damaging the uncured hose persist when any excessive feeding force must be applied.
These problems are further complicated by the extremely limp characteristics of the hose. The aforementioned forces that resist entrance of the hose into a pressurized curing zone can cause the limp hose to bend along its axis even when small feeding forces are applied.